[poopstang]

hello all, i'm new to site and need to ask a question. i own a 90 5.0 mustang and need some wiring help. I installed a master battery disconnect and having trouble shutting car down. i want to hook my fuel pump and MSD to switch, so whole car can be shut down by switch. seems like altenator is giving switch power after switch is shut off, and car still runs. when i remove alt wire from soleniod, the switch shuts down everything the way i want, cuts off MSD and shuts off fuel pump. but with feed wire from alt. still connected to soleniod everything still runs when i turn switch off. does anyone know of a relay or a certain schematic or trouble shooting of this problem. the reason why i'm asking is because i need to make the car track legal, and i want to cut off spark and fuel from a click of a master switch

[tbird]

Certain brand battery switches have an extra set of small terminals next to the big ones on the back of the switch. These can be used to cut the power to the ignition. You need to hook up the small 12v activation wires that turn the MSD on to these terminals. Do not hook the large power wires to the MSD ,that will not work. When the swtch is turned off it will turn off the MSD box regardless of weather or not the alternator is backfeeding the car.

[poopstang]

so i don't have to run the alt. wire to the master switch? would that be easier? instead of running the 12v wires?

[poopstang]

also thanks for repling alot of help to me...:thumbsup

[tbird]

No,by killing the ignition the engine will stop and so will the alternator thereby eliminating any back feeding problems caused by the alternator still charging.